I'm kludging together a plasma torch, some rollers and a steel frame to make a machine that can cut 42" OD (or smaller) steel pipe. The machine will not only cut but it will have the potential to bevel the cut (i.e. for welding two pieces of pipe together).

I'm sort of working on a design that has an electric motor attached to what amounts to a small tire via a chain drive to rotate the pipe. Right now I'm guessing a 5hp, 220VAC 3 phase motor. I'll have to check against another machine that does a similar job, but with a saw blade (and no beveling).

The wall thickness of the pipe will be around 1/2" or less, so I'm not worried about the plasma, but I'm trying to keep this as simple as possible, both for operation and maintenance. I've got somewhere between $1000-2000 USD for controls and the motor.

What I'd like to do is literally have a "volume" knob where a user will set the volume to the wall thickness of the pipe...so there will be settings for 1/8", 3/16", 1/4", 3/8", 1/2", 5/8" and 3/4"...faster for 1/8", slower for 3/4".

Is a VFD a good solution for this project? I can set the knob to deliver signals to the vfd based on the settings, and perhaps use a microcontroller to do it digitally if necessary...but I'd rather do it analog. Keeping it simple, stupid and all that rot.

Thoughts?